Gas generation for a missile post-boost control system

ABSTRACT

A gas generator for a missile includes a propellant grain, inhibitor, internal insulation, case forward and aft closures, external insulation, igniters and a gas outlet assembly. The general steps for manufacturing the gas generator are to fabricate the components and assemble the case including the external and internal insulation. The cylindrical inhibitor is then attached to the forward closure to form a cavity into which the propellant is cast forming a sleeve around it when assembled. This propellant grain assembly is then inserted into the case, and the forward closure, igniter and gas outlet assembly are then attached to the case to form a complete gas generator. When the gas generator is ignited, the propellant is consumed by burning the solid material into hot gases which escape through the gas outlet assembly. The propellant contains its own fuel and oxidizers to provide the necessary energy.

FIELD OF THE INVENTION

This invention relates to gas generators and more particularly, butwithout limitation thereto, to solid propellant gas generators for usein post-boost control systems of guided missiles.

BACKGROUND OF THE INVENTION

Because of increased performance requirements relating to missilesystems and the gas generators used for propulsion energy requirementsthere is a continuing search for new techniques for generating largemasses of gas at high pressure. These gas generators are used in missilepost-boost control systems, for example, to provide gas energy to thecontrol system thrust nozzles for forward, reverse, pitch, yaw and rollcontrol. Prior techniques have not provided the high performancerequired for advanced weapon systems that must undergo severe operatingenvironments and have requirements for longer periods of high pressuregases and at minimum weight. These and other requirements have beenaccomplished by the gas generator design of the present invention.

OBJECTIVES OF THE INVENTION

An object of the present invention is to provide a solid propellant gasgenerator to withstand the severe operating conditions of a missilesystem.

Still another object of the present invention is to provide the highenergy gas requirements of missile systems.

A further object of the present invention is to provide an efficient,reliable and cost effective gas generator design for a missile system.

A still further object of the present invention is to provide a solidpropellant gas generator that has high gas flow, high operatingpressure, high operating temperatures, long burn time duration, andwhich operates efficiently, reliably and with optimum safety.

SUMMARY OF THE INVENTION

These objects of the invention and other objects, features andadvantages to become apparent as the specification progresses areaccomplished by the invention according to which, briefly stated, a gasgenerator includes a propellant grain, inhibitor, internal insulation,case forward and aft closures, external insulation, igniters and a gasoutlet assembly. The general steps for manufacturing the gas generatorare to fabricate the components and assemble the case including theexternal and internal insulation. The cylindrical inhibitor is thenattached to the forward closure to form a cavity into which thepropellant is cast forming a sleeve around it when assembled. Thispropellant grain assembly is then inserted into the face, and theforward closure, igniter and gas outlet assembly are then attached tothe case to form a complete gas generator. When the gas generator isignited, the propellant is consumed by burning the solid material intohot gases which escape through the gas outlet assembly. The propellantcontains its own fuel and oxidizers to provide the necessary energy. Asthe propellant burns, the length and weight of the propellant grain, ofcourse, decreases.

LIST OF ADVANTAGES OF THE INVENTION

An important advantage of the present invention is to provide alightweight, high pressure, long duration, efficient gas generator thathas a removable propellant grain assembly. Moreover, all of the adversestructural and thermal environments are resolved by the gas generatordesign of the present invention.

These and further objectives, constructional and operationalcharacteristics, and advantages of the invention will no doubt be moreevident to those skilled in the art from the detailed description givenhereinafter with reference to the figures of the accompanying drawingswhich illustrate a preferred embodiment by way of non-limiting example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of the gas generator assembly of the presentinvention.

FIG. 1A is a cross-sectional view taken of the forward section alongsection line 1A--1A of FIG. 2.

FIG. 1B is a cross-sectional view taken of the aft section along sectionline 1B--1B of FIG. 3.

FIG. 2 is the forward view taken at view line 2--2 of FIG. 1.

FIG. 3 is the aft view taken at view line 3--3 FIG. 1.

FIG. 4 is a cross-sectional view taken at section line 4--4 of FIG. 1A.

FIG. 5 is a partial cross sectional view taken along section line 5--5of FIG. 3.

GLOSSARY

The following is a glossary of elements and structural members asreferenced and employed in the present invention.

    ______________________________________                                        11          gas generator                                                     13          propellant grain                                                  15          inhibitor                                                         17          internal insulation                                               19          case                                                              21          external insulation                                               23          internal insulation                                               25          forward closure                                                   27          external insulation                                               29          gas outlet assembly                                               31          igniter assembly                                                  33          aft dome section                                                  34          thickened forward section of case 19                              35, 37, 39, 41                                                                            attachment lugs                                                   43          thickened section of forward enclosure 25                         45          o-ring groove                                                     47          annular retaining key groove                                      49          handling holes                                                    51          retaining key                                                     53          o-ring                                                            55, 57, 59, 61, 63                                                                        silica phenolic insulation section                                65, 67, 69, 71                                                                            molybdenum liners                                                 73          external outlet insulation                                        75          titanium elbow casting                                            77          columbium reducer                                                 83          gas diffuser for igniter 31                                       85          air gap                                                           ______________________________________                                    

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals are usedto designate like or corresponding parts throughout the various figuresthereof, there is shown in FIG. 1 a side elevation view of the gasgenerator assembly of the present invention as indicated by referencenumeral 11. FIG. 2 is the forward view as taken as 2--2 of FIG. 1 andFIG. 3 is the aft view taken at 3--3 of FIG. 1.

Generator 11 includes propellant grain 13, inhibitor 15, internalinsulation 17, case 19, all of which are cylindrical in configuration.The latter three are in a concentric sleeve arrangement with theexternal insulation 21. The forward insulation comprises three majorsegments. The forward section is domed shaped and includes internalinsulation 23, forward closure 25, and external insulation 27. The aftsection shown in FIGS. 1B and 3 is domed shaped and has gas outletassembly 29 and igniter assembly 31 attached to the exterior thereof.

The propellant grain is made from a hydroxyl terminated polybutadrienepolymer propellant with HMX solid particles used as oxidizer (HTPB/HMX)composite propellant with flame temperature of nearly 3,000° F. Thepropellant weight is approximately 232 pounds and is cast into acylindrical inhibitor 15 to form a cylindrical propellant grain having alength of about 29 inches and a diameter of about 13 inches. The grainis an end burning design with a configured start up surface for addedinitial burn area and uniform flame front propagation.

Case 19 is made from 6Al-4V titanium alloy and is of cylindricalconfiguration with an integral half dome section 33, an enlarged forwardsection 34 and attachment lugs 35, 37, 39, and 41. Forward closure 25 ismade from 6Al-4V titanium alloy, has a domed configuration, thickenedsection 43, o-ring groove 45, retaining key groove 47 and four handlingholes 49. The forward closure is removably attached to the case with aretaining key 51 and is sealed by means of a o-ring 53. FIG. 4 shows theforward retention assembly including an opening 54 formed in attachmentlug 37 wherein a flexible retaining key 51 is inserted therethrough andinto annular retaining groove 47 to lock forward titanium closure 25 tothe forward section 34 of titanium case 19. See FIG. 1A.

The radial interface between the exterior surface of the inhibitor 15and the interior surface of the insulator 17 is an interference fithaving no clearance. This is done to maximize propellant weight, assuremechanical integrity, and eliminate separation of the inhibitor and thepropellant grain during gas generator operation. Elimination of thisseparation is critical to prevent propellant burn-back in theinterference region between the grain surface and the inhibitor. Thepropellant grain assembly is loaded and unloaded by cooling the grainassembly to provide necessary clearance between the inhibitor andinsulator and then subjecting the assembly to normal temperatureconditions where the interface achieves an interference fit.

As shown in FIG. 1B, gas outlet assembly 29 includes internal silicaphenolic insulation sections 55, 57, 59, 61 and 63, molybdenum liners65, 67, 69, and 71, external outlet insulation 73, titanium elbowcasting 75 and columbium reducer 77. This particular design allowsassembly of thick insulation sections 55-63 which permits a long burntime of hot high pressure gases.

FIG. 5 shows igniter assembly 31 which is attached to the aft domesection 33 of the case. The igniter assembly contains a propellant whichgenerates hot gases that are emitted through gas diffuser 83 thatextends into air gap 85 between the aft end of the propellant and theinsulator 17. These hot gases ignite the propellant which discharges itsgases through gas outlet assembly 29.

The constituents and process of the propellant to inhibitor bondingsystem of the present invention are as follows:

(1) The above described inhibitor and forward closure assembly (whichcontains insulation 23) are assembled and placed into casting tooling.The inhibitor 15 and interior insulation 23 are made of the samematerial and generally comprise an ethylene propylene, diene monomer(EPDM/neoprene rubber binders containing silica powder and aramidfibers.) The specific chemical composition is set forth in Tables I andII as follows:

                                      TABLE I                                     __________________________________________________________________________    (Chemical Composition)                                                                                By Weight                                                                     Composition in Parts per 100                                                  Parts of Rubber Binder (PHR)                          Function                                                                              Ingredient      Minimum                                                                            Maximum                                                                             Nominal                                    __________________________________________________________________________    Binder  EPDM Elastomer  79.0 81.0  80.0                                               2 Chlorobutadiene                                                                             19.0 21.0  20.0                                               1,3 Elastomer                                                         Filler  Silica Hydrate  29.0 31.0  30.0                                       Antioxidants                                                                          Polymerized Trimethyl                                                                         1.9  2.1   2.0                                                Dihydroquinoline                                                              Alkylated Diphenylamines and                                                                  0.9  1.1   1.0                                                Diphenyl-P-Phenylendiamene                                            Curing Agent                                                                          40% a,a' Bis (Tert-Butylperoxy)                                                               5.5  5.7   5.6                                                Diisopropylbenzene                                                    Processing Aids                                                                       Napthenic Process Oil                                                                         4.9  5.1   5.0                                                Synthetic Polyterpene Resin                                                                   4.9  5.1   5.0                                        Fiber   Aramid Fiber (.25 inch)                                                                       27.0 29.0  28.0                                       Activator                                                                             Zinc Oxide, Technical                                                                         4.9  5.1   5.0                                        __________________________________________________________________________

                                      TABLE II                                    __________________________________________________________________________    (Functional Description of Ingredients)                                       Ingredient      Description                                                   __________________________________________________________________________    EPDM Elastomer  EPDM elastomer; binder also adds chemical                                     bond sites                                                    2 Chlorobutadiene 1,3 Elastomer                                                               Choroprene elastomer added to improve                                         processing and bonding                                        Silica Hydrate  Mineral filler to improve thermal                                             properties (mixing and packing)                               Polymerized Trimethylquinoline                                                                Polymerized trimethylquinoline antioxidant                                    prevents aging degradation of the polymer                                     chain                                                         Alkylated Diphenylamines and                                                                  Diphenylamine; antioxidant used in combination                Diphenyl-p-Phenylendiamine                                                                    with above for high temperature storage                                       conditions                                                    40% a,a' Bis (Tert-Butylperoxy),                                                              40% active peroxide supported on Burgess                      Diisopropylbenzene (curative)                                                                 KE clay; curative for both polymers also                                      provides aging stability as compared to                                       Sulfur, for example.                                          Napthenic Process Oil                                                                         Lubricating oil; improve mixing                               Synthetic Polyterpene Resin                                                                   Tackifier added to improve green tack                                         (adhesion between uncured layers)                             Aramid Fiber (.25 inch)                                                                       Aramid fiber reinforcement; improved char                                     retention and thermal properties                              Zinc Oxide      Activator for curing agent                                    __________________________________________________________________________

The following are the process steps used to prepare the uncured thermalinsulation and inhibitor composition.

(1) The initial batch includes mixing the binders, antioxidants,processing aids and catalyst. A Banbury mixer is used for approximately8 to 10 minutes (10 minutes optimum).

(a) The fiber filler is then mixed with the step (1) constituents. ABanbury mixer is used for three submixes each for approximately oneminute.

(b) The curative is then mixed with the step (a) constituents. A Banburymixer is used for approximately one minute to form a slab about 4 inchesthick, one foot wide and from one to two feet long.

(c) The mixed slab of step (b) is then calendered to about 0.1 inchthick.

(d) The calendered material of step (c) is then remixed in a Banburymixer for about one minute to form a mixed slabs as defined in step (b).

(e) The mixed slab of step (d) is then calendered to about an 0.1 inchthick sleet having an approximate 4 foot width.

(f) A thin plastic cover sheet is applied to one surface of the step (6)uncured insulation sheet and rolled for subsequent use.

(g) When used; the uncured insulation is cut to proper configuration;the configured insulation is laid up and the plastic sheet is removed.If additional insulation thickness is required another piece of uncuredinsulation is cut to proper configuration and laid up against the firstuncured insulation sheet and the plastic sheet is removed. The first andsecond sheets are tacky and are pressed together to form contiguousinsulation sheets. The process is repeated until the total desireduncured insulation thickness is achieved.

(h) The uncured insulation of step (g) is then cured by subjecting it toelevated temperatures wherein the time and temperature is dependent uponthe total thickness of uncured insulation. The inhibitor sleeve has anominal thickness of about 150 mils, a length of about 30 inches and adiameter of about 13 inches.

(2) The inner surface of the cavity formed by inhibitor sleeve 15 andinsulator 23 is cleaned with a methyl ethyl ketone (MEK) dampened lintfree cloth and is then dried for at least 60 minutes.

(3) A barrier coat is then brush applied to the interior surface of thecleaned cavity. The barrier coat is an epoxy resin with amine curingagent, such as Scotchcast-8™ (made by The Minnesota Mining andManufacturing Co.). The barrier coat is brush applied to a nominalweight of about 0.35 pounds or about 3-4 mils thickness.

(4) The barrier coat is then cured wherein the cure time and temperatureis 24 hours minimum at 60° to 90° F. plus 1 hour minimum at 170°±5° F.

(5) A liner is then brush coated onto the cured interior surface of thebarrier coat. The inhibitor sleeve and forward closure are preheated to170° F. for 2 to 6 hours prior to liner application. The liner isapplied in two brush coats and has a final nominal weight of about 0.25pounds or 2-3 mils. thickness. The chemical composition of the liner iscarbon black, isophorone diisocyanate liquid, polybutadiene liquidhydroxyl terminated (type II), and ferric acetylacetonate. The mixingprocess of the uncured liner material is as follows:

(a) Add polybutadiene liquid hydroxyl terminated (type II) and ferricacetylacetonate to mixer and blend 1 hour minimum at low speed with mixtemperature 160°±10° F. Cool to 90°±10° F. before further processing.

(b) Add isophorone diisocyanate and blend 10 minutes minimum at lowspeed.

(c) Screen carbon black through a 100 mesh screen using Ro-Tap withapproximately 5 mm diameter glass beads. Add approximately 1/3 of thecarbon black to mix and blend for 10 minutes minimum at low mixer speed.Repeat mixing step for each of the two remaining portions of carbonblack.

(d) When all ingredients have been added and mixed, run mixer at lowspeed for 60 minutes minimum under vacuum of 25 inches of mercuryminimum. Mix temperature shall not exceed 90° F. Break vacuum withnitrogen or argon.

(e) Clean storage cans and lids with solvent and allow to air dry.Transfer mix to 1 quart cans, or 1 pint cans. Purge cans with nitrogenor argon before filling. After filling, flush with nitrogen or argonbefore installing lids.

(f) Store in deep freeze at 0°±10° F.

(6) The liner is then cured for a total time of 72 to 96 hours at atemperature of 170° F.±5° F. If propellant casting operations are not tobegin immediately purge with nitrogen and seal. The lined assembly maybe stored up to 2 weeks maximum before casting at 60° to 90° F.

(7) The propellant is manufactured and then cast into the lined cavity.The propellant materials are HMX Class I, carbon black, isophoronediisocyanate, and polybutadiene liquid hydroxyl terminated (type II).

(a) The mixing process of the uncured propellant begins by adding thepolybutadiene liquid hydroxyl terminated (type II) and the carbon blackto mixer. The carbon black shall be added within 4 hours maximum ofremoval from "in use" storage. Blend the ingredients for 5 minutes atatmospheric pressure and then under vacuum for 15 minutes at a minimumvacuum of 28 inches of mercury. The vacuum shall be broken withnitrogen. While mixing, add ground Class 1 HMX utilizing a vibratingfeeder. This mixing shall be for a minimum of 40 minutes at atmosphericpressure. While mixing, add the unground Class 1 HMX utilizing avibrating feeder. This mixing shall be for a minimum of 45 minutes atatmospheric pressure followed by blending for a minimum of 1 hour at aminimum vacuum of 28 inches mercury. Vacuum shall be broken withnitrogen.

(b) Removed sample for moisture analysis and total solids test.

(c) Add IPDI, mix 10 to 12 minutes, at atmospheric pressure. Blend undervacuum at a minimum vacuum of 28 inches of mercury for 90 minutes.During the final mixing, the mixer shall be run at its slowest speed andthe water jacket temperature adjusted to yield a final mix temperatureof 140°±5° F. Break vacuum with nitrogen. The propellant shall be castwithin 10 hours maximum upon completion of mixing.

(d) The casting process of the uncured propellant begins by preheatingthe casting hardware assembly 2 to 6 hours at 170°±100° F. prior tocasting if not already hot from the liner cure.

(e) The hopper is loaded with propellant and replenished as necessaryduring casting. The hopper water jacket temperature is maintained at140°±10° F. and relative humidity is maintained at 30 to 60% duringcasting.

(f) The inhibitor sleeve/closure assembly is evacuated to a pressure ofnot less than 5 mm of mercury. Close off vacuum line to inside ofinhibitor sleeve, but maintain vacuum on outside of inhibitor sleeve toprevent sleeve from collapsing during casting. Open hopper valve toallow propellant to flow into inhibitor sleeve, allowing pressure in thesleeve to be not more than 20 mm of mercury until the propellant levelis approximately 1 inch from bottom of casting tooling "clamp" ring,discontinue breaking vacuum and add propellant to obtain correct heightof maximum of 2 inches from bottom of "clamp" ring. Close hopper valveand break vacuum. Remove casting hopper and measure propellant level. Ifinsufficient propellant, replace casting hopper, evacuate the sleeve toa pressure of not more than 120 mm of mercury and cast additionalpropellant. Release vacuum on inside of sleeve first, then releasevacuum on outside of sleeve.

(g) The propellant is then cured, thereby bonding the propellant toliner inhibitor 15, by sealing the end of the casting cylinder andapplying nitrogen gas at a pressure of 40±5 psig for the first 60 hoursminimum of cure. The propellant shall be cured for a total time of 140to 164 hours at 170° F.±5° F. Total deviations from propellant curetemperature totaling one hour are permitted provided that the excursiontemperatures are greater then 40° F. and less than 200° F. Totaldeviations in excess of one hour and less than 12 hours are permittedprovided the excursion temperatures are less than 130° F. and greaterthan 90° F. The total propellant cure time is to be extended by thetotal time of propellant cure temperature excursion below 165° F.

(h) The nitrogen gas is released and the grain assembly allowed to cool1 hour minimum after cure.

After the above described manufacturing and curing process the assemblyis then machined as previously described and as shown in the FIG. 4.

Because of the severe temperature, time, pressure and load conditionsput on a gas generator of the type described it is critical that themetal case to non-metal bonding system be effective under adverseconditions. The present invention provides such a bonding system thedetails of which are as follows:

(1) The titanium case (6AL-4V) is sandblasted with a 180 grit aluminumoxide abrasive to a surface roughness not to exceed 125 microinches.

(2) The interior sandblasted surface is then cleaned by using a lintfree cloth dampened in methyl ethyl ketone (MEK) solvent.

(3) A corrosion resistant coating is then applied such as Chemlok 205™(rubber to metal adhesive primer made by Lord Chemical Products) bybrush application and having a nominal thickness of 1-2 mils. Chemlok205™, for example, is a chlorinated resin and phenolic blend in 79%solvent with 5% titanium oxide and 1% zinc oxide.

(4) The corrosion resistant coating is then air dried at ambienttemperature and atmosphere for at least 60 minutes.

(5) A metal to rubber adhesive coating is then applied using an adhesivesuch as Chemlok 252™ by brush application and leaving a nominalthickness of 1-2 mils. Chemlok 252™, for example, is a chlorinated resinwith EPDM rubber curing agent.

(6) The Chemlok 252™ adhesive coating is then air dried at ambienttemperature and atmosphere for at least 60 minutes.

(7) Uncured insulation material is then laid up against the interiorsurface of the air dried adhesive coating. Several layers are used untilthe desired insulation characteristics (defined by thickness or weight)are achieved. Each layer adheres to the next since the uncured materialis tacky. Between each layer a vacuum bag is inserted and a vacuum ispulled between the bag and the insulation material to attach adjacentlayers of material. The insulation material preferable has plasticbacking for storage and handling purposes.

A specific example of the lay-up process for the sheets of uncuredinsulation is as follows:

1. For the metal aft dome insulation cut five patterns, four patterns ofapproximately 0.100 inch thick and 1 additional pattern (thickness asrequired of insulating material). Pattern sizes are nominal in inches asfollows:

                  TABLE III                                                       ______________________________________                                        Pattern OD (in.)     ID (in.) Thickness (in.)                                 ______________________________________                                        1       14.60        2.670    .100                                            2       14.60        2.425    .100                                            3       14.70        2.290    .100                                            4       14.75        2.155    .100                                            5       14.80        2.030    As required                                     ______________________________________                                    

2. For the metal case insulation cut five patterns of approximately0.100 inch thick insulating material. Pattern sizes are nominal ininches as follows:

                  TABLE IV                                                        ______________________________________                                                         Length (in.)                                                 Pattern    Width (in.) Bottom    Top                                          ______________________________________                                        1          26 13/16    451/4     451/2                                        2          26          45        44 11/16                                     4          251/2       431/4     433/4                                        5           61/2       421/4     421/2                                        ______________________________________                                    

The grain direction of the insulation material shall run axially withthe motor case.

3. Lay dome patterns on table and clean top side with MEK and allow toair dry 10 minutes minimum.

4. Place patterns 1 and 2 clean sides mating into a dome preformfixture. Leave plastic backing on the outsides.

5. Place patterns 3 and 4 in similar condition. Remove plastic backingfrom outside of pattern 4 and clean with MEK. Allow to air dry 10minutes minimum. Place pattern 5, clean, unprotected side on pattern 4.Leave plastic backing on outsides of patterns 3 and 5. Place patternsinto a dome preform fixture.

6. Place mold assembly into a press and pressurize to 5-8 tons for 5-8minutes minimum. Allow insulating material to stay in mold until needed.

7. Remove dome insulation from fixture. Remove the plastic backing andclean with MEK. Allow to air dry 10 minutes minimum.

8. Place pattern into the case first, locating the edge the distancefrom case retaining key groove. Smooth the pattern against the inside ofcase. Wipe the pattern surface with MEK and allow to air dry 10 minutesminimum. Filter circulating air is to be used for approximately 2minutes.

9. Install conventional cure ring in case. Install an oven film bag andfasten to cure ring with vacuum sealer or equivalent. Attach vacuumlines to fittings on cure ring and elbow connector and pull vacuum (24inch Hg) for 10 minutes minimum.

10. Remove cure ring, oven film bag and vacuum lines. Cure ring may beleft in place.

11. Install two ply dome insulation piece into case. Align insulationhole with entrance to outlet.

12. Pull vacuum per Steps 9 and 10.

13. Install remaining dome insulation piece into case per steps 11 and12.

14. Install remaining patterns individually per steps 9 and 10.

15. Using new O-rings, install case cure ring into end of case andinstall conventional retaining key cure plug. Place teflon glass fabricon dome and side wall full length. Install cure bag into gas generatorcase. Secure cure bag to cure ring with rubber strip and hose clamp.Remove gas generator case assembly from handling fixture and place oncart and secure. Install ortman key plug and apply vacuum sealer orequivalent to all sealing areas of case.

16. Pull vacuum of 24 inches Hg for 30 minutes minimum. Ensure that curebag has all the wrinkles out, is seated correctly and there are noleaks. This step may be performed after installation into an autoclavebut prior to the start of the heating of the autoclave.

17. Move case to the autoclave. Place gas generator case on cure cartand install in autoclave.

18. The insulation, adhesive and casing are now cured which results in abonding between the case and insulation. A specific example of theautoclave curing process is as follows:

(a) Attach vacuum line from pump to vacuum fitting on case outlet.

(b) With assembly under a vacuum of 24 inches of mercury minimum, startheating autoclave to 160° F.±10° F. and maintain for 2.0-3.0 hours attemperature.

(c) Start air compressor and pressurize assembly to 125-145 psig andincrease the temperature to 195° F.±10° F. Maintain temperature andpressure for 1.5-2.0 hours.

(d) Increase autoclave temperature to 325° F.±10° F. and maintain for3.5-4.0 hours. NOTE: Any deviation from the required temperaturetolerance of 10° F. or less for a total of 15 minutes or less will beacceptable as long as the actual cure time to the required temperatureis within the required cure time tolerance except when the temperaturedeviates above the temperature requirement.

(e) Maintain 125-145 psig until autoclave temperature reaches 150° F.This cool down period shall not be less than 30 minutes.

(f) Release pressure, remove assembly from autoclave and allow to coolto ambient.

(g) Remove all fittings, cure bag, and glass fabric from gas generatorcase. Clean case as necessary using MEK.

19. After the completion of step 18 the interior surface is machined tofinal dimensions for receiving the propellant grain assembly.

This invention has been described in detail with particular reference toa certain preferred embodiment, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention. This invention is not limited to the preferredembodiment and alternatives heretofore described, to which variationsand improvements may be made, without departing from the scope ofprotection of the present patent and true spirit of the invention, thecharacteristics of which are summarized in the following claims.

What is claimed is:
 1. A gas generator comprising:a cylindrical chamber,said chamber having a domed forward section, a domed aft section, saidaft section having a centrally located aft round oriface; a cylindricalpropellant grain having one end abutting said forward section and theopposite end spaced from said aft section; an outlet assembly connectedto said aft section and communicating with said aft opening; and saidcylindrical chamber including a cylindrical case, said aft section beingintegral with said case, said case and aft section being formed oftitanium.
 2. The gas generator of claim 1 wherein said outlet assemblyincludes a plurality of thick insulation sections that are inserted intothe outlet assembly to permit long burn time of hot, high pressuregases.